40 DISEASES OF FIELD & GARDEN CROPS. [OH. 



they appear in nearly every kitchen-garden, where they 

 are grown for flavouring soups, and as ingredients for 

 salads. They are much milder than " scallions," i.e., 

 thickly-sown onions, which have no room allowed for the 

 formation of bulbs. 



At Fig. 1 2 is engraved a fragment of a scape or flower- 

 stem of an affected plant of chives, 

 enlarged five diameters, to illustrate 

 the enormous number of disease 

 pustules with which the flower stem, 

 together with every other part of a 

 diseased plant, is covered. It is 

 curious that the scapes are first and 

 most affected. When these pustules 

 or ulcers are examined with a strong 

 lens they look like little masses of 

 brownish dust distinctly growing 

 beneath the epidermis of the host 

 plant. As the disease runs its 

 course, and these pustules enlarge 

 in size, they burst open the epi- 

 dermis, and the brown or blackish 

 X'5- matter, in the form of fine dust, is 



FIG. 12 get free in the air r^ p ustu i es 



NEW DISEASE OF ONIONS. , .. , ., 



Pucdnia mixta, Fi. Frag- or masses of brown dust-like spores, 

 ment of flower scape of for such they are, are technically 



chives. Enlarged 5 dia- ca j le ^ ^ f rom tte Greek, SOWS, a 

 meters. , 



heap. 



To understand the nature of the brown dust contained in 

 the sori, a very small sorus must be selected and removed 

 from the leaf ; then, with a keen lancet, it must be cut 

 either transversely or longitudinally in two, and the ex- 

 posed surface examined. The illustration at Fig. 1 3 repre- 

 sents a transverse section through one of the smallest sori, 

 viz. a disease speck, only one-hundredth of an inch across, 

 magnified 200 diameters. The transparent epidermis of 

 the scape is seen broken at AA, and some of the constituent 



